Method for the catalytic reduction of acid chlorides and imidoyl chlorides

Abstract

The present application relates to methods for the catalytic reduction of acid chlorides and/or imidoyl chlorides. The methods comprise reacting the acid chloride or imidoyl chloride with a silane reducing agent in the presence of a catalyst such as [Cp(Pr i 3 P)Ru(NCMe) 2 ] + [PF 6 ] − .

1 . A method for the catalytic reduction of a compound selected from an acid chloride and an imidoyl chloride, the method comprising reacting the compound with a silane reducing agent in the presence of a catalyst of Formula I: 
       
         
           
           
               
               
           
         
       
       wherein
 Cp x  is unsubstituted η 5 -cyclopentadienyl or η 5 -cyclopentadienyl substituted with 1 to 5 methyl groups; 
 R 1 , R 2  and R 3  are each independently selected from C 1-6 alkyl and C 6-10 aryl; 
 R 4  and R 5  are each independently C 1-4 alkyl; and 
 X −  is a counteranion. 
 
     
     
         2 . The method of  claim 1 , wherein Cp x  is unsubstituted η 5 -cyclopentadienyl. 
     
     
         3 . The method of  claim 1 , wherein the silane reducing agent is selected from dimethylphenylsilane, triethylsilane, methylphenylsilane and triphenylsilane. 
     
     
         4 . The method of  claim 3 , wherein the silane reducing agent is dimethylphenylsilane. 
     
     
         5 . The method of  claim 1 , wherein R 1 , R 2  and R 3  are each isopropyl. 
     
     
         6 . The method of  claim 1 , wherein R 4  and R 5  are each CH 3 . 
     
     
         7 . The method of  claim 1 , wherein X −  is selected from [PF 6 ] − , [ClO 4   − ], [B[3,5-(CF 3 ) 2 C 6 H 3 ] 4 ] − , [B(C 6 F 5 ) 4 ] − , [Al(OC(CF 3 ) 3 ) 4 ] − , a carborane-based counteranion and a non-nucleophilic amide counteranion. 
     
     
         8 . The method of  claim 1 , wherein the catalyst of Formula I is [Cp(Pr 1   3 P)Ru(NCMe) 2 ] + [PF 6 ] − . 
     
     
         9 . The method of  claim 1 , wherein the compound is an acid chloride having the structure: 
       
         
           
           
               
               
           
         
       
       wherein R 6  is
 C 1-10 alkyl, optionally substituted with chloro; 
 C 6-14 aryl, optionally substituted with halo, nitro or C 1-4 alkoxy, 
 heteroaryl; or 
 —C(O)OR 7 , wherein R 7  is C 1-6 alkyl. 
 
     
     
         10 . The method of  claim 1 , wherein the compound is an acid chloride having the structure: 
       
         
           
           
               
               
           
         
       
       wherein R 8  is C 1-10 alkylene, C 6-14 arylene or heteroarylene. 
     
     
         11 . The method of  claim 1 , wherein the compound is an imidoyl chloride having the structure: 
       
         
           
           
               
               
           
         
       
       wherein
 R 9  is C 1-10 alkyl or is C 6-14 aryl, optionally substituted with C 1-4 alkoxy; and 
 R 10  is C 1-6 alkyleneC 6-14 aryl or is C 6-14 aryl, optionally substituted with a —C(O)R 11  group or a —C(O)OR 12  group, wherein R 11  and R 12  are, independently, C 1-6 alkyl. 
 
     
     
         12 . The method of  claim 1 , wherein the catalyst is present in an amount of from about 0.2 mol % to about 20 mol %, based on the amount of the compound being reduced. 
     
     
         13 . The method of  claim 1 , wherein the reaction of the compound with the silane reducing agent is carried out in the presence of at least one solvent. 
     
     
         14 . The method of  claim 13 , wherein the solvent is selected from chloroform, dichloromethane, acetone and acetonitrile. 
     
     
         15 . The method of  claim 13 , wherein the solvent is selected from chloroform, dichloromethane and acetone. 
     
     
         16 . The method of  claim 15 , wherein the reaction of the compound with the silane reducing agent is further carried out in the presence of a C 1-6 alkyl cyanide. 
     
     
         17 . The method of  claim 16 , wherein the C 1-6 alkyl cyanide is tBuCN or CH 3 CN. 
     
     
         18 . The method of  claim 17 , wherein the C 1-6 alkyl cyanide is present in an amount of from about 5 mol % to about 250 mol %, based on the amount of the compound being reduced. 
     
     
         19 . The method of  claim 1 , wherein the silane reducing agent is present in an amount of about 1 equivalent to about 2 equivalents, based on the amount of a functional group being reduced. 
     
     
         20 . The method of  claim 1 , wherein the catalyst of Formula I is generated in situ from the reaction of a catalyst precursor of Formula II: 
       
         
           
           
               
               
           
         
       
       wherein
 Cp x  is unsubstituted η 5 -cyclopentadienyl or η 5 -cyclopentadienyl substituted with 1 to 5 methyl groups; 
 R 4 , R 5  and R 13  are each independently C 1-4 alkyl; and 
 X −  is a counteranion, 
 
       with a phosphine of Formula III: 
       
         
           
           
               
               
           
         
       
       wherein
 R 1 , R 2  and R 3  are each independently selected from C 1-6 alkyl and C 6-10 aryl. 
 
     
     
         21 . The method of  claim 1 , wherein the reaction of the compound with the silane reducing agent in the presence of the catalyst of Formula I is carried out at a temperature of about 20° C. to about 25° C.